1. Field of the Invention
The present invention relates to an improvement of a fluid transmitting device with a lock-up clutch, in which a plurality of damper springs are arranged in an annular shape and housed in an annular spring housing groove formed in a clutch piston of a lock-up clutch, a plurality of first transmitting claws each inserted between corresponding adjacent ones of the damper springs are provided to the clutch piston, and a plurality of second transmitting claws each facing a corresponding one of the first transmitting claws and inserted between the adjacent damper springs are provided to a turbine impeller.
2. Description of the Related Art
The applicant has already proposed a structure of such a fluid transmitting device with a lock-up clutch by which the second transmitting claws can be manufactured with a good yield and are applicable in common to various fluid transmitting devices of different specifications, leading to a remarkable reduction in cost, and in the welding of the second transmitting claws to the turbine impeller, the quantity of heat applied to the turbine impeller can be minimized, thereby suppressing the thermal strain of the turbine impeller. In the structure, each of the second transmitting claws is formed of: a claw portion inserted between the adjacent damper springs; and a substantially rectangular base portion integrally connected to the root of the claw portion, and having its long side arranged in the peripheral direction of the turbine impeller and its short side arranged in the axial direction of the turbine impeller. Moreover, both short-side portions of the base portion are fixed to the turbine impeller by welding (see Japanese Patent Application Laid-open No. 2003-148590).
However, in the fluid transmitting device with a lock-up clutch having the above structure, there may be an increase in the stress concentrated at the spots where the second transmitting claws are welded to the turbine impeller, due to improvement in engine output performance. Thus, reinforcing the welding spots has become necessary. To this end, it is conceivable to increase the thickness of each second transmitting claw, but doing so increases the weight of the second transmitting claw and eventually increases the weight of the transmitting device. Such an increase will affect the fuel consumption of the engine.